1. Field of the Invention
The present invention relates to a hydrodynamic bearing assembly that can ensure the reliability of oil sealing and a motor having the same.
2. Description of the Related Art
A small-sized spindle motor, which is used in a recording disc driving device, uses a hydrodynamic bearing assembly. While oil is disposed between a shaft and a sleeve of the hydrodynamic bearing assembly, the shaft is driven by fluid pressure generated by the oil.
In line with improved performance of recording disc driving devices, the demand for low current, low Non Repeatable Run Out (NNRO), impact resistance and vibration resistance has increased.
Furthermore, as a shaft rotates at high speed, research into oil sealing has been conducted in order to solve the problems wherein the oil inside the hydrodynamic bearing assembly splashes outside the hydrodynamic bearing assembly.
Meanwhile, in the hydrostatic assembly, an upper or lower end of a shaft hole in a sleeve, into which a shaft is inserted, is tapered so that oil undergoes taper sealing.
The bearing span of the shaft is decreased due to the above-described taper sealing, so that it becomes difficult for the shaft to stably support a rotor.
In recent years, as a sintered sleeve containing large amounts of oil has been used, oil interfaces have greatly varied due to the thermal expansion of the oil. Taper sealing that allows for changes in the oil interfaces is required to prevent overflow of the oil, which makes it more difficult to support the rotor.